The present invention relates to a method of checking or testing the assembled state of an internal combustion engine.
When the assembling of an internal combustion engine (hereinafter, referred to as the xe2x80x9cenginexe2x80x9d) finishes, it is necessary to judge whether there is a fault with the assembling of the engine, such as missing of any part of the engine, or asynchronism of respective operations of two or more parts of the same. If the engine has a fault, it cannot perform as designed. One example of the assembled engine testing method is disclosed in U.S. Pat. No. 5,355,713. In the disclosed method, an assembled engine is rotated in a xe2x80x9ccoolxe2x80x9d state in which no fuel is fired, a pressure waveform is obtained from an exhaust-valve or intake-valve side space of the engine, and the obtained pressure waveform is compared with a reference pressure waveform which is obtained in advance from a normal engine. Thus, whether or at not there is a fault with the assembling of the engine is judged. The U.S. patent discloses the technique of comparing a characteristic of the obtained waveform with a corresponding characteristic of the reference waveform. The characteristic may be the amplitude of at least one of a (positive) pressure pulse and a vacuum (negative pressure) pulse contained in each pressure waveform. In addition, the U.S. patent discloses the technique of judging that an assembled engine has a fault if the pressure in the exhaust-valve side space of the engine (hereinafter, referred to as the xe2x80x9cexhaust pressurexe2x80x9d) does not exceed a reference value at a predetermined angular phase of a crank shaft of the engine (hereinafter, referred to as the xe2x80x9ccrank-shaft (CS) anglexe2x80x9d) where the exhaust pressure would exceed the reference value if the engine were normal. That is, the engine testing method disclosed in the U.S. patent consists in comparing a measured characteristic value of exhaust or intake pressure of an assembled engine, such as maximal or minimal value or a value corresponding to a particular CS angle, with a reference value obtained from a normal engine.
The U.S. patent teaches finding a fault with an assembled engine based on a pressure waveform obtained from either one of the exhaust-valve or intake-valve side space of the engine. However, it fails to teach finding a fault based on respective pressure waveforms obtained from the exhaust-valve and intake-valve side spaces of the engine. In addition, if the disclosed method finds a fault, it ends. Therefore, if an assembled engine has different sorts of faults, the method cannot find those faults.
It is therefore an object of the present invention to provide an assembled engine testing method which is different from that disclosed in the above-identified U.S. patent.
According to a first aspect of the present invention, there is provided a method of testing an assembled internal combustion engine having an intake valve and an exhaust valve, being characterized by rotating the assembled engine, measuring a timing of occurrence of at least one predetermined condition of a pressure in at least one of an external intake-valve side space which communicates with the intake valve and an external exhaust-valve side space which communicates with the exhaust valve, and judging, based on the measured timing, whether there is at least one fault with the assembling of the engine.
In the testing method in accordance with the first aspect of the invention, the timing of occurrence of the at least one predetermined condition of the pressure in the intake-valve side space or the external exhaust-valve side space (hereinafter, referred to as xe2x80x9cthe intake pressurexe2x80x9d or the xe2x80x9cexhaust pressurexe2x80x9d) changes depending upon the changing pressure in a cylinder (hereinafter, referred to as the xe2x80x9ccylinder pressurexe2x80x9d) in which a piston reciprocates linearly and the opening and closing timings of the intake and exhaust valves. The cylinder pressure increases as the piston moves up toward its top dead position, and decreases as the piston moves down toward its bottom dead position. In the reciprocating engine, after the intake and exhaust valves close, first, the exhaust valve starts opening and subsequently the intake valve starts opening. After the exhaust valve closes, the intake valve closes. During each cycle, if, e.g., the timing of commencement of opening of the intake valve is earlier (i.e., corresponds to a smaller CS angle) than a reference timing obtained from a normal engine, the exhaust pressure takes a maximal value smaller than a reference value obtained from the normal engine and takes a less time to reach the maximal value. To the contrary, if the timing of commencement of opening of the intake valve is later (i.e., corresponds to a larger CS angle) than the reference timing obtained from the normal engine, the exhaust pressure takes a maximal value greater than the reference value and takes a more time to reach the maximal value. Therefore, if, e.g., the timing when the exhaust pressure takes a maximal value is known, the relationship between the opening and closing timings of the intake valve and the CS angle is known. Thus, it can be judged that the assembled engine has the assembling fault of an incorrect phase difference between a crank shaft and a cam shaft. In addition, if, e.g., the opening and closing timings of the exhaust valve change relative to the CS angle, the change influences the intake pressure. Thus, the fault of incorrect phase difference between the crank and cam shafts can be identified based on the timing of occurrence of at least one predetermined condition of the intake pressure. In this way, it is possible to judge whether there is at least one fault with an assembled engine, based on the timing of occurrence of one or more predetermined conditions of the intake pressure and/or the exhaust pressure, without having to take the engine apart. The present testing method does not exclude finding an assembling fault by taking into account an intake or exhaust pressure value corresponding to the predetermined condition. For example, an exhaust pressure value at the timing when the exhaust valve starts opening, a maximal value of the exhaust pressure, etc. may be taken into account. The assembled engine may be rotated in a xe2x80x9chotxe2x80x9d state, i.e., by firing of fuel therein, or in a xe2x80x9ccoolxe2x80x9d state, i.e., by being connected to a separate rotating device and compulsorily rotated by the device. Generally, the xe2x80x9ccoolxe2x80x9d test is easier than the xe2x80x9chotxe2x80x9d test. In the hot test, it is cumbersome to supply fuel to the engine and treat the exhaust gas emitted therefrom. In addition, in the xe2x80x9chotxe2x80x9d test, the pressure signals obtained from the intake-side and exhaust-side spaces contain more noise. The xe2x80x9ccoolxe2x80x9d test is free from those problems, and accordingly can be carried out more easily.
According to a preferred feature of the first aspect of the invention, the judging step comprises comparing the measured timing with a reference timing and judging, based on the comparison result, whether there is at least one fault with the assembling of the engine. The reference timing may be a timing which is actually measured from a normal engine having no assembling fault, or may be a timing which is prescribed by a designer. An incorrect phase of a crank shaft may be caused by an incorrect relative phase between the crank shaft and a crank pulley due to inappropriate attachment of the pulley to the shaft, an incorrect relative phase between the crank pulley and a timing belt or chain due to inappropriate engagement thereof, etc. An incorrect phase of a cam shaft may be caused by an incorrect relative phase between the cam shaft and a cam pulley due to inappropriate attachment of the cam pulley to the cam shaft, an incorrect relative phase between the cam pulley and a timing belt or chain due to inappropriate engagement thereof, etc. As will be described later on the preferred embodiments, the incorrect phase of the cam shaft may also be caused by an incorrect relative phase between a drive gear attached to one of an intake cam shaft for operating the intake valves and an exhaust cam shaft for operating the exhaust valves, and a driven gear attached to the other cam shaft. The timing of occurrence of the predetermined condition of the exhaust or intake pressure discontinuously changes due to the presence of each of the above faults, because the amount of deviation of the incorrect phase of the crank pulley, etc. from its correct phase stepwise changes. Similarly, the timing of occurrence of the predetermined condition discontinuously changes due to missing of a compression ring. Therefore, the reference timing with which the measured timing is compared may be a timing of occurrence of the predetermined condition which is measured from one or more normal engines each having no assembling fault. Therefore, if the difference between the measured timing and the reference timing falls in a reference range, the assembled engine may be judged as normal, i.e., having no assembling fault. On the other hand, the timing of occurrence of the predetermined condition continuously changes due to the presence of an incorrect intake-valve or exhaust-valve clearance. Therefore, if the clearance of an intake or exhaust valve falls in a reference range, the valve may be judged as normal. In the last case, the reference value with which the measured value is compared corresponds to every value within the reference range. In any case, the reference value is used as a criterion for distinguishing an engine having at least one fault from an engine having no fault. Therefore, whether there is at least one fault with an assembled engine can be judged quickly and easily by comparing the measured timing of occurrence of the predetermined condition, with the reference timing.
According to another feature of the first aspect of the invention, the measuring step comprises measuring at least one of a first timing when the exhaust pressure in the exhaust-valve side space takes a maximal value; a second timing when the exhaust pressure changes from a first is decreasing state to a constant state in which the exhaust pressure does not change as time elapses; a third timing when the exhaust pressure changes from the constant state to a second decreasing state; a fourth timing when the intake pressure in the intake-valve side space takes a maximal value; and a fifth timing when the intake pressure changes from a constant state in which the intake pressure does not change as time elapses, to an increasing state. The first to fifth timings are very reliable for finding at least one assembling fault, because at each of those timings the exhaust or intake pressure significantly changes. Therefore, each of those timings can be measured with high accuracy, and one or more faults can be found with high reliability.
According to another feature of the first aspect of the invention, the judging step comprises identifying at least one fault with the assembling of the engine based on at least one of a positive or negative sign and an absolute value of a difference between at least one measured timing out of the first to fifth timings and a corresponding one of a first, a second, a third, a fourth, and a fifth reference timing.
According to another feature of the first aspect of the invention, the judging step comprises identifying at least one fault with the assembling of the engine based on a combination of a plurality of measured timings out of the first to fifth timings each of which measured timings is different from a corresponding one of a first, a second, a third, a fourth, and a fifth reference timing.
According to another feature of the first aspect of the invention, the at least one fault comprises at least one of an incorrect clearance of the intake valve; an incorrect clearance of the exhaust valve; an incorrect relative phase between a crank shaft and a cam shaft; and a missing of a compression ring. The four assembling faults occur most frequently. As will be described later by reference to the preferred embodiments of the invention, it is possible to identify at least two faults out of those four faults, based on the measured timing of at least one predetermined condition of the intake pressure and/or the exhaust pressure. Since those faults actually occur frequently in assembly lines, it is very efficient to be able to find one or more of those faults without having to take the engine apart.
According to another feature of the first aspect of the invention, the incorrect relative phase between the crank shaft and the cam shaft comprises at least one of an incorrect relative phase between the crank shaft and a crank pulley; an incorrect relative phase between a cam pulley and the cam shaft; and an incorrect relative phase between a drive gear and a driven gear.
According to another feature of the first aspect of the invention, the testing method further comprises the step of closing at least one of an exhaust-valve side passage which connects between the exhaust valve and an exhaust manifold and an intake-valve side passage which connects between the intake valve and an intake manifold, wherein the at least one of the external exhaust-valve side space and the external intake-valve side space comprises at least one of an exhaust-valve side portion of the closed exhaust-valve side passage and an intake-valve side portion of the closed intake-valve side passage. In this case, the reliability of the engine testing method is improved. It is possible to measure the exhaust or intake pressure without having to close the exhaust-valve side passage which connects between the exhaust valve and the exhaust manifold, or the intake-valve side passage which connects between the intake valve and the intake manifold. However, in the case where the exhaust-valve side passage and/or intake-valve side passage are/is closed, it is possible to detect accurately a change of the exhaust or intake pressure which results from the presence of one or more assembling faults, and accurately measure the timing of occurrence of at least one predetermined condition of the exhaust or intake pressure. Thus, the present testing method enjoys an improved reliability. In this case, it is preferred to carry out the testing method before the exhaust manifold and/or the intake manifold are/is attached to the engine.
According to another feature of the first aspect of the invention, the at least one of the external intake-valve side space and the external exhaust-valve side space comprises the exhaust-valve side space which comprises an exhaust-valve room and an exhaust manifold whose outlet is closed. In each cycle of operation of an engine having a plurality of cylinders, the opening and closing of the exhaust valve or valves of each of the cylinders sequentially occur at a regular interval of timing. As will be described later on the preferred embodiments, if the pressure in a single space provided by the exhaust-valve room and an inner space of the exhaust manifold is detected, then it can be judged whether there is at least one fault with each cylinder of the engine. Since in this case the testing method can be carried out after the exhaust manifold has been assembled, the exhaust pressure of each cylinder can be detected more easily.
According to another feature of the first aspect of the invention, the at least one of the external intake-valve side space and the external exhaust-valve side space comprises an internal space of a surge tank. In each cycle of operation of an engine having a plurality of cylinders, the opening and closing of the intake valve or valves of each of the cylinders sequentially occur at a regular interval of timing, like the opening and closing of the exhaust valve or valves of each cylinder. As will be described later on the preferred embodiments, if the pressure in the inner space of the surge tank is detected, then it can be judged whether there is at least one fault with each cylinder of the engine. Since in this case the testing method can be carried out after the intake manifold and the surge tank have been assembled and the number of pressure sensors employed can be minimized, the intake pressure of each cylinder can be detected very easily.
According to another feature of the first aspect of the invention, the judging step comprises identifying at least two faults out of a plurality of faults of the engine which result from the assembling thereof. In the case where a plurality of assembling faults occur to a single engine, the testing method in accordance with the first aspect of the invention may identify only the presence of one or more faults out of the plurality of faults. Otherwise, if it identifies of what kind is one fault found, then the test may be over with the identified fault being displayed. In contrast, in the testing method in accordance with the present feature, at least two faults are simultaneously identified. In the case where only the presence of one or more faults is identified, an operator must take the engine apart and identify the fault or faults. In the case where the engine test is terminated when a fault is identified, the operator must correct the fault displayed and again carry out the same test on the engine for identifying another possible fault and correcting the second fault. In either case, it takes a long time to remove the fault or faults from the engine. In contrast, if at least two faults out of the plurality of faults with the engine can be simultaneously identified, those identified faults can be simultaneously removed. If all the faults with the engine can be simultaneously identified, all those faults can be simultaneously removed. The last case is ideal. However, it is not essentially required that all the faults with the engine be simultaneously identified. It is sufficiently efficient to identify simultaneously at least two faults out of the plurality of faults with the engine. In addition, if the total number of faults which the engine may have with any possibility can be limited or reduced to a smaller one based on the measured timing, the time needed to identify the fault or faults with the engine can be accordingly reduced.
According to another feature of the first aspect of the invention, the at least one predetermined condition of the pressure can occur at a plurality of timings corresponding to a plurality of faults which can result from the assembling of the engine, and wherein the judging step comprises identifying at least one of the plurality of faults, based on at least one of (a) an amount of deviation of the measured timing of the at least one predetermined condition from a reference timing and (b) a combination of at least two predetermined conditions whose measured timings are deviated from at least two reference timings, respectively.
According to another feature of the first aspect of the invention, the testing method further comprising the step of deciding, when a measured timing of each of at least two predetermined conditions of the pressure is equal to a reference timing, that there is no fault with the assembling of the engine, and omitting carrying out the judging step. In this case, the judging step is prevented from being carried out uselessly.
According to another feature of the first aspect of the invention, the plurality of timings comprise at least one timing which corresponds to each of at least two faults of the plurality of faults, and wherein the identifying step comprises utilizing one of the plurality of timings which corresponds to a smallest number of faults, prior to the other timings. In the case where a plurality of faults can simultaneously occur to a single engine, the present testing method can easily identify at least one fault out of the plurality of faults. If the measured timing of occurrence of a certain predetermined condition is judged as being different from the reference timing by, e.g., being compared with one of the plurality of timings which corresponds to the smallest number of faults (e.g., one), the smallest number of faults can be identified easily. The thus identified fault or faults can be utilized for identifying another or other remaining fault or faults.
According to another feature of the first aspect of the invention, the identifying step comprises utilizing one of the plurality of timings which corresponds to at least one fault the identification of which is most easily confirmed by an an operator, prior to the other timings. If the correctness of identification of at least one fault can be confirmed by an operator, then it can be utilized for identifying another or other remaining fault or faults. The easier the confirmation is, the easier the employment of this identifying manner is.
According to another feature of the first aspect of the invention, the identifying step comprises utilizing one of the plurality of timings which corresponds to at least one fault which is most easily corrected by an operator, prior to the other timings. In the case where a plurality of faults occur to a single engine, if at least one fault out of the plurality of faults is identified and corrected, one or more remaining faults can be identified more easily, or one or more faults which have been judged as being not identifiable turn to be identifiable.
According to another feature of the first aspect of the invention, the rotating step comprises rotating, using an independent rotating device, a crank shaft of the assembled engine and thereby reciprocating a piston of the engine in a cylinder of the engine, while the at least one of the intake-valve side and exhaust-valve side spaces is isolated from an atmosphere, and wherein the judging step comprises judging whether there is at least one fault with an assembled state of the engine, based on at least one of (a) a pressure in the one of the intake-valve side and exhaust-valve side spaces which is measured while a corresponding one of the intake and exhaust valves is closed and (b) at least one of a starting and an ending timing of a closed state of one of the intake and exhaust valves which corresponds to the one of the intake-valve side and exhaust-valve side spaces.
According to another feature of the first aspect of the invention, the rotating step comprises rotating, using an independent rotating device, a crank shaft of the assembled engine and thereby reciprocating a piston of the engine in a cylinder of the engine, while the at least one of the intake-valve side and exhaust-valve side spaces is isolated from an atmosphere, and wherein the judging step comprises judging whether there is at least one fault with an assembled state of the engine, based on at least one of (a) a pressure in the one of the intake-valve side and exhaust-valve side spaces which is measured while a corresponding one of the intake and exhaust valves is closed and (b) at least one of a starting and an ending timing of a closed state of one of the intake and exhaust valves which corresponds to the one of the intake-valve side and exhaust-valve side spaces.
According to another feature of the first aspect of the invention, the assembled engine includes a plurality of cylinders each of which has an intake valve and an exhaust valve, wherein the measuring step comprises measuring, for each of at least two cylinders of the plurality of cylinders, at least one of (a) a value of a pressure in at least one of an external intake-valve side space which communicates with the intake valve corresponding to the each cylinder and an external exhaust-valve side space which communicates with the exhaust valve corresponding to the each cylinder, when the pressure satisfies the at least one predetermined condition, and (b) a timing at which the pressure satisfies the at least one predetermined condition, wherein the method further comprises a step of comparing the at least one of the value and the timing of a first one of the at least two cylinders with the at least one of the value and the timing of a second one of the at least two cylinders, and wherein the judging step comprises judging that there is at least one fault with the assembling of the engine, when the at least one of the value and the timing of the first cylinder is not equal to the at least one of the value and the timing of the second cylinder.
According to a second aspect of the present invention, there is provided a method of testing an engine including a cylinder, a piston, a crank shaft, an intake valve and an exhaust valve, characterized by rotating, using an independent rotating device, the crank shaft and thereby reciprocating the piston in the cylinder, while at least one of an external intake-valve side space which communicates with the intake valve and an external exhaust-valve side space which communicates with the exhaust valve is isolated from an atmosphere, and evaluating a state of the engine based on at least one of (a) a pressure in the one of the intake-valve side and exhaust-valve side spaces which is measured while a corresponding one of the intake and exhaust valves is closed and (b) at least one of a starting and an ending timing of a closed state of one of the intake and exhaust valves which corresponds to the one of the intake-valve side and exhaust-valve side spaces.
The engine testing method in accordance with the second aspect of the invention may be carried out on an engine which is provided with an ignition plug. In this case, the method can be carried out without having to remove the ignition plug from the engine. If the method is performed with the intake and exhaust valves being closed, the inner space of the cylinder is isolated from not only the intake-valve side and exhaust-valve side spaces but the atmosphere. In the case where the method is performed with the intake-valve side space being isolated from the atmosphere, the intake-valve side space is completely isolated if the intake valve or valves is or are completely closed, so that the pressure in the intake-valve side space becomes constant irrespective of the reciprocation of the piston. Similarly, in the case where the method is performed with the exhaust-valve side space being isolated from the atmosphere, the exhaust-valve side space is completely isolated if the exhaust valve or valves is or are completely closed, so that the pressure in the exhaust-valve side space becomes constant irrespective of the reciprocation of the piston. Since it is easy to detect the constant-pressure state of the intake-valve side or exhaust-valve side space, it is also easy to find one or more faults with the engine based on the detection result. For example, it is easy to find the fault of incomplete valve closing, that is, the fault that an intake or exhaust valve does not completely close because, e.g., a foreign matter bites into the space between the intake or exhaust valve and a corresponding valve seat. If the incomplete valve closing or the foreign-matter biting occurs, the pressure of the intake-valve side space (xe2x80x9cthe intake pressurexe2x80x9d) or the pressure of the exhaust-valve side space (xe2x80x9cthe exhaust pressurexe2x80x9d) which would be constant if the engine would be normal changes as the pressure of the inner space of the cylinder (xe2x80x9cthe cylinder pressurexe2x80x9d) changes with the rotation of the crank shaft. Therefore, if a change of the intake or exhaust pressure is detected at a timing when the intake or exhaust pressure should be constant, it can be judged that the engine being tested has the fault of incomplete valve closing. In addition, since it is easy to detect the constant state of the intake or exhaust pressure, it is also easy to detect the starting and ending timings of the constant state of the intake or exhaust pressure. Since the starting and ending timings correspond to the opening and closing timings of the intake or exhaust valve, it is easy to determine the opening and closing timings, indirectly based on the starting and ending timings. However, the opening and closing timings of the intake or exhaust valve may be determined directly by using an exclusive valve-position sensor or sensors. Moreover, the intake or exhaust pressure is naturally raised when the piston reciprocates in the cylinder and the pressurized air in the inner space of the cylinder is supplied to the intake-valve side or exhaust-valve side space. Thus, the present method does not need an exclusive pressure source for changing the intake or exhaust pressure. The present method may be carried out on an engine just after the engine has been assembled from various parts in a factory, or when the engine is overhauled after some use.
According to a first preferred feature of the second aspect of the invention, the one of the intake-valve and exhaust-valve side spaces comprises the exhaust-valve side space, and the evaluating step comprises evaluating the state of the engine based on the pressure in the exhaust-valve side space which is measured while the exhaust valve should have been closed.
According to a second preferred feature of the second aspect of the invention, the evaluating step comprises judging that the exhaust valve has incompletely been closed, when the pressure in the exhaust-valve side space changes while the exhaust valve should have been closed.
According to a third preferred feature of the second aspect of the invention, the judging step comprises judging that the exhaust valve has incompletely been closed, when the pressure in the exhaust-valve side space measured while the exhaust valve should have been closed is higher than a first reference value.
According to a fourth preferred feature of the second aspect of the invention, or according to any one of the above-indicated first to third preferred features, the one of the intake-valve and exhaust-valve side spaces comprises the exhaust-valve side space, and the evaluating step comprises judging that the intake valve has incompletely been closed, when the pressure in the exhaust-valve side space measured while the exhaust valve is open is lower than a second reference value. In the case where the exhaust pressure is measured in the manner in which the exhaust-valve side space is isolated from the atmosphere and the intake-valve side space is communicated with the atmosphere, both the cylinder pressure and the exhaust pressure are raised as the piston is moved up with the exhaust valve being opened and the intake valve being closed, because air is compressed in both the inner space of the cylinder and the exhaust-valve side space. However, if the intake valve has not completely closed, the air in the inner space of the cylinder partly flows into the atmosphere via the intake valve, so that the exhaust pressure takes a maximum value lower than that taken when the intake valve is normal. Thus, the present method can identify the fault of incomplete intake-valve closing.
According to a fifth preferred feature of the second aspect of the invention, or according to any one of the above-indicated first to fourth preferred features, the evaluating step comprises a state-change-timing depending evaluating step for evaluating the state of the engine based on the at least one of the starting and ending timings of the closed state of the one of the intake and exhaust valves which corresponds to the one of the intake-valve side and exhaust-valve side spaces which is isolated from the atmosphere, the at least one of the starting and ending timings of the closed state of the one valve comprising at least one of a first state-change timing when the pressure in the one space changes from a changing state to a constant state and a second state-change timing when the pressure in the one space changes from the constant state to the changing state.
According to a sixth preferred feature of the second aspect of the invention, the pressure-change-timing depending evaluating step comprises evaluating the state of the engine based on an interval between the first and second state-change timings. The occurrence or presence of one sort of fault may change or move both the first and second state-change timings in the same direction along the axis of time, and the presence of another sort of fault may move the first and second state-change timings in the opposite directions. Therefore, one or more faults may be identified based on the interval between the first and second state-change timings. In addition, since this interval depends on all the faults that influence at least one of the first and second state-change timings, it is possible to identify, based on the single amount (i.e., the interval), a fault which influences both of the two timings.
According to a seventh preferred feature of the second aspect of the invention, or according to any one of the above-indicated first to sixth preferred features, the rotating step comprises an opposite-direction rotating step for rotating, using the independent rotating device, the crank shaft of the engine in an opposite direction opposite to a normal direction in which the crank shaft is rotated when the engine is actually operated by firing. In the case where the engine is rotated by the independent rotating device, the engine can be easily rotated in the opposite direction, so that information can be obtained which cannot be obtained when the engine is rotated in the normal direction. Thus, one or more bad states of the engine which cannot be identified based on only the information obtained when the engine is rotated in the normal direction, can be identified based on the information obtained when the engine is rotated in the opposite direction. In addition, the reliability of evaluation of one or more bad states of the engine can be improved based on the information obtained when the engine is rotated in the opposite direction. The opposite-direction rotating step may be carried out independent of the first or second aspect of the invention. In the last case, too, the step provides the same advantages.
According to an eighth preferred feature of the second aspect of the invention, the opposite-direction rotating step comprises rotating the crank shaft of the engine in the opposite direction while the intake-valve side space is isolated from the atmosphere. This opposite-direction rotating step is symmetrical with the normal-direction rotating step in which the exhaust-valve side space is isolated from the atmosphere and the engine is rotated in the normal direction. Accordingly, for example, the order of opening of the intake and exhaust valves is reversed. Thus, very important information can be obtained.
According to a ninth preferred feature of the second aspect of the invention, or according to any one of the above-indicated first to eighth preferred features, the rotating step comprises a normal-direction rotating step for rotating, using the independent rotating device, the crank shaft of the engine in a normal direction in which the crank shaft is rotated when the engine is actually operated by firing.
According to a tenth preferred feature of the second aspect of the invention, the opposite-direction rotating step comprises rotating the crank shaft of the engine in the normal direction while the exhaust-valve side space is isolated from the atmosphere. In this engine testing method, various sorts of useful information can be obtained, and one or more bad states of the engine can be identified based on the information.
According to an eleventh preferred feature of the second aspect of the invention, or according to any one of the above-indicated first to tenth preferred features, the testing method further comprising the step of isolating, using a valve which is selectively opened and closed, the at least one of the intake-valve side and exhaust-valve side spaces from the atmosphere. In this case, the intake-valve side and/or exhaust-valve side spaces are easily isolated from the atmosphere, by closing one or more valves provided for the space or spaces. Therefore, the efficiency of the engine tests is improved.
According to a third aspect of the present invention, there is provided a method of testing an assembled internal combustion engine including a plurality of cylinders each of which has an intake valve and an exhaust valve, characterized by rotating the assembled engine, measuring, for each of at least two cylinders of the plurality of cylinders, at lest one of (a) a value of a pressure in at least one of an external intake-valve side space which communicates with the intake valve corresponding to the each cylinder and an external exhaust-valve side space which communicates with the exhaust valve corresponding to the each cylinder, when the pressure satisfies a predetermined condition, and (b) a timing at which the pressure satisfies the predetermined condition, comparing the at least one of the value and the timing of a first one of the at least two cylinders with the at least one of the value and the timing of a second one of the at least two cylinders, and judging that there is at least one fault with the assembling of the engine, when the at least one of the value and the timing of the first cylinder is not equal to the at least one of the value and the timing of the second cylinder.
In the testing method in accordance with the third aspect of the invention, the timing at which the pressure in the intake-valve side space or the external exhaust-valve side space (hereinafter, referred to as xe2x80x9cthe intake pressurexe2x80x9d or the xe2x80x9cexhaust pressurexe2x80x9d) satisfies the predetermined condition changes depending upon the changing pressure in a cylinder (hereinafter, referred to as the xe2x80x9ccylinder pressurexe2x80x9d) in which a piston reciprocates linearly and the opening and closing timings of the intake and exhaust valves. The cylinder pressure increases as the piston moves up toward its top dead position, and decreases as the piston moves down toward its bottom dead position. In the reciprocating engine, after the intake and exhaust valves close, first, the exhaust valve starts opening and subsequently the intake valve starts opening. After the exhaust valve closes, the intake valve closes. During each cycle, if, e.g., the timing of commencement of opening of the intake valve is earlier (i.e., corresponds to a smaller CS angle) than a reference timing obtained from a normal engine, the exhaust pressure takes a maximal value smaller than a reference value obtained from the normal engine and takes a less time to reach the maximal value. To the contrary, if the timing of commencement of opening of the intake valve is later (i.e., corresponds to a larger CS angle) than the reference timing obtained from the normal engine, the exhaust pressure takes a maximal value greater than the reference value and takes a more time to reach the maximal value. Therefore, if, e.g., the timing when the exhaust pressure takes a maximal value is known, the relationship between the opening and closing timings of the intake valve and the CS angle is known. Thus, it can be judged that the assembled engine has the assembling fault of an incorrect phase difference between a crank shaft and a cam shaft. In addition, if, e.g., the opening and closing timings of the exhaust valve change relative to the CS angle, the change influences the intake pressure. Thus, the fault of incorrect phase difference between the crank and cam shafts can be identified based on the timing of occurrence of at least one predetermined condition of the intake pressure. In this way, it is possible to judge, without having to take the engine apart, whether there is at least one fault with the assembled engine, based on at least one of the value of the intake and/or exhaust pressure when the pressure satisfies the predetermined condition, and the timing at which the pressure satisfies the predetermined condition. In the present engine testing method, one or more assembling faults of the engine is or are found by measuring, for at least two cylinders, at least one of a value of the pressure when the pressure satisfies the predetermined condition and a timing at which the pressure satisfies the predetermined condition, and comparing the pressure value and/or timing obtained for one cylinder with the pressure value and/or timing obtained for another or the other cylinder. For example, there are some cases where the pressure value obtained for an abnormal cylinder having an assembling fault is different from that obtained for a normal cylinder. If the difference is detected, it can be judged that one of those two or more cylinders has an assembling fault. If this comparison is made among more cylinders, more information about the assembled state of the engine can be obtained. Thus, one or more cylinders having an assembling fault can be specified with higher accuracy. Since in this method it is not necessary to determine CS angles corresponding to the pressure values and/or timings obtained for the cylinders, an apparatus for carrying out the method can enjoy a simpler construction. As far as the present invention is concerned, the term xe2x80x9ccomparingxe2x80x9d encompasses judging whether there is a significant difference between the combination of respective values of a plurality of parameters obtained for one cylinder and that obtained for another cylinder and, in the last case, the term xe2x80x9cequalxe2x80x9d means that all the respective values of the combination for the first cylinder are equal to those of the combination for the second cylinder. The present method does not exclude finding an assembling fault by comparing a value of the intake or exhaust pressure when the pressure satisfies the predetermined condition with respect to each cylinder, with a reference value obtained from one or more normal engines. For example, the maximal value of the exhaust pressure obtained from each cylinder may be compared with a reference maximal value obtained from normal engines. The assembled engine may be rotated in a xe2x80x9chotxe2x80x9d state, i.e., by firing of fuel therein, or in a xe2x80x9ccoolxe2x80x9d state, i.e., by being connected to a separate rotating device and compulsorily rotated by the device. Generally, the xe2x80x9ccoolxe2x80x9d test is easier than the xe2x80x9chotxe2x80x9d test. In the hot test, it is cumbersome to supply fuel to the engine and treat the exhaust gas emitted therefrom. In addition, in the xe2x80x9chotxe2x80x9d test, the pressure signals obtained from the intake-side and exhaust-side spaces contain more noise. The xe2x80x9ccoolxe2x80x9d test is free from those problems, and accordingly can be carried out more easily.
According to a first preferred feature of the third aspect of the invention, the assembled engine includes a first bank having at least one cylinder, and a second bank having at least one cylinder, wherein the comparing step comprises comparing the at least one of the value and the timing of the at least one cylinder of the first bank with the at least one of the value and the timing of the at least one cylinder of the second bank. For example, if a fault occurs to the phase of the cam shaft of one of two banks of a V-type engine, the pressure value and/or timing obtained for a cylinder of the one bank corresponding to the cam shaft having the fault is different from the pressure value and/or timing obtained for a cylinder of the other bank corresponding to the cam shaft having no fault. The present method can find at least one fault which can occur to each one of the two banks independent of the other bank.
According to a second preferred feature of the third aspect of the invention, or the above-indicated first preferred feature, the comparing step comprises comparing the at least one of the value and the timing of each of the at least two cylinders with at least one of an average of the respective values of the at least two cylinders and an average of the respective timings of the at least two cylinders. The pressure value or the timing obtained for each cylinder may change by various amounts, including a very small or large one, corresponding to various sorts of assembling faults. Those changes may include not only changes corresponding to faults but also changes resulting from measurement errors. It is preferable to remove the latter changes. The present engine testing method can reduce the influences of the latter changes, thereby finding at least one fault with improved accuracy.
According to a third preferred feature of the third aspect of the invention, or the above-indicated first or second preferred feature, the comparing step comprises dividing the at least two cylinders into at least two groups including a first group including at least one cylinder and a second group including at least one cylinder the at least one of the value and the timing of which significantly differs from the at least one of the value and the timing of the at least one cylinder of the first group, and comparing the at least one of the value and the timing of the at least one cylinder of the first group with the at least one of the value and the timing of the at least one cylinder of the second group. The present engine testing method enjoys the same advantage as that of the method according to the second preferred feature of the invention.
According to a fourth preferred feature of the third aspect of the invention, or any of the above-indicated first to third preferred features, the measuring step comprises measuring, for every one of the plurality of cylinders, a timing at which the pressure satisfies the predetermined condition, and the comparing step comprises comparing a time interval between respective times when the respective pressures of a first pair of successively firing cylinders of the plurality of cylinders satisfy the predetermined condition, with a time interval between respective times when the respective pressures of a second pair of successively firing cylinders of the plurality of cylinders satisfy the predetermined condition. As will be described in connection with the preferred embodiments of the invention, one or more faults which occur at a very high frequency can be easily detected by the simple method in which a time interval between respective times when the respective pressures of a first pair of successively firing cylinders satisfy the predetermined condition, with a time interval between respective times when the respective pressures of a second pair of successively firing cylinders satisfy the predetermined condition. Those faults include faults with the respective clearances of the intake and exhaust valves. In the case where the engine being tested includes two banks, those faults additionally include faults with the respective cam pulleys and respective driven gears of the two banks.
According to a fifth preferred feature of the third aspect of the invention, or any of the above-indicated first to fourth preferred features, the measuring step comprises measuring, for every one of the plurality of cylinders, at least one of (a) a value of the pressure when the pressure satisfies the predetermined condition and (b) a timing at which the pressure satisfies the predetermined condition.
According to a sixth preferred feature of the third aspect of the invention, or any of the above-indicated first to fifth preferred features, the comparing step comprises dividing the at least two cylinders into at least two groups including a first group including at least two cylinders and a second group including at least two cylinders the at least one of the value and the timing of each one of which significantly approximates to the at least one of the value and the timing of the other or another cylinder of the at least two cylinders of the second group and significantly differs from the at least one of the value and the timing of each of the at least two cylinders of the first group, and comparing the at least one of the value and the timing of each of the at least two cylinders of each of the first and second groups with the at least one of the value and the timing of the other or another cylinder of the at least two cylinders of the each group.
According to a seventh preferred feature of the third aspect of the invention, or any of the above-indicated first to sixth preferred features, the measuring step comprises measuring, for every one of the plurality of cylinders, a value of the pressure when the pressure satisfies the predetermined condition, and the comparing step comprises comparing the respective values of every pair of successively firing cylinders of the plurality of cylinders, with each other.
According to an eighth preferred feature of the third aspect of the invention, or any of the above-indicated first to seventh preferred features, the predetermined condition comprises at least one of a first condition that the exhaust pressure in the exhaust-valve side space takes a maximal value; a second condition that the exhaust pressure is in a constant state in which the exhaust pressure takes a constant value as timing elapses; a third condition that the exhaust pressure changes from the constant state to a decreasing state; a fourth condition that the intake pressure in the intake-valve side space takes a maximal value; and a fifth condition that the intake pressure changes from a constant state in which the intake pressure takes a constant value as timing elapses, to an increasing state.
According to a ninth preferred feature of the third aspect of the invention, the value of the pressure when the pressure satisfies the predetermined condition comprises at least one of the maximal value and the constant value.
According to a tenth preferred feature of the third aspect of the invention, or the above-indicated eighth preferred feature, the timing at which the pressure satisfies the predetermined condition comprises at least one of a timing at which the first condition occurs; a timing at which the second condition starts; a timing at which the third condition occurs; a timing at which the fourth condition occurs; a timing at which the fifth condition occurs.